A physical model study investigated alternatives to improve ice passage at the Soo Locks in Sault Ste. Marie, Michigan. This paper describes the ice problems at the Soo Locks and the solutions developed in the study. Model tests were conducted to evaluate the performance of high-flow air curtains to deflect ice pushed ahead of vessels entering the 366-m-long Poe Lock. A series of air curtains and an array of point source bubblers were also tested to break ice jams in the upper approach of the adjacent MacArthur Lock. In addition, an array of high-flow point source bubblers was developed in the model to relieve ice congestion in front of the downstream miter gates of the Poe Lock. A model water cannon was also found effective for clearing ice in front of miter gates and breaking jams in the upper lock approach.Key words: Soo Locks, physical model study, ice passage, winter navigation, Great Lakes, high-flow air curtain, point source bubbler, miter gate, water cannon.